<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="../dist/css/bootstrap.min.css">
  <link rel="stylesheet" href="../dist/bootstrap-icons.css">
  <title>副标题</title>
</head>
<body>
  <h2>
    二级标题
    <small class="text-muted">副标题</small>
  </h2>
  <h3>
    三级标题
    <small class="text-muted">副标题</small>
  </h3>
</body>
</html>